Which of the following devices acts as a switch within a flat-panel detector to release the electric charge collected by the detector element?

The thin-film transistor (TFT) functions as a switch in a flat-panel detector by controlling the release of the electric charge that has been collected by the detector element. In a flat-panel detector, each pixel consists of a detector element that absorbs radiation and generates an electric charge. The TFT is integrated into the pixel circuitry and plays a crucial role in readout processes; specifically, it enables the charge to be transferred to the corresponding readout electronics at the appropriate time.

By rapidly switching on and off, the TFT helps coordinate the timing of charge collection and readout, allowing for high-quality imaging with minimal noise. Without the TFT acting as this switch, the management of electric charges in the array of detector elements would be inefficient, potentially leading to blurring or other image quality issues.

The other options do not serve this switching function in the same way. For example, photodiodes are sensors that convert light into an electrical signal but do not operate as switches. Photomultiplier tubes amplify light signals but are not used in modern flat-panel detector technology for this purpose. Storage capacitors temporarily hold electric charge, but they rely on the TFT to release the charge to the readout system effectively. Thus, the TFT's role is vital in ensuring